How to select and mount MOSIONX ball-screw support units: fixed vs supported end, sizing by shaft diameter, bearing match and alignment tolerances.
The fixed end (BK / EK / FK) carries the full axial force, radial force and bending moment — use a zero-clearance or preloaded bearing and lock it reliably. The supported end (BF / EF / FF) gives radial location and rotation support, allowing slight axial float for thermal growth.
| Shaft Ø (mm) | Fixed-end options | Supported-end options | Fixed bearing | Supported bearing |
|---|---|---|---|---|
| 6 | EK-6 | EF-6, FF-6 | 706ATYDF | 606ZZ |
| 8 | EK-8, FK-8 | EF-8, FF-8 | 708ATYDF | 606ZZ |
| 10 | BK-10, EK-10, FK-10 | BF-10, EF-10, FF-10 | 7000ATYDF | 608ZZ |
| 12 | BK-12, EK-12, FK-12 | BF-12, EF-12, FF-12 | 7001ATYDF | 6000ZZ |
| 15 | BK-15, EK-15, FK-15 | BF-15, EF-15, FF-15 | 7002ATYDF | 6002ZZ |
| 17 | BK-17 | BF-17 | 7203ATYDF | 6203ZZ |
| 20 | BK-20 / EK-20, FK-20 | BF-20 / EF-20, FF-20 | 7004ATYDF / 7204ATYDF | 6004ZZ / 6204ZZ |
| 25 | BK-25, EK-25, FK-25 | BF-25, EF-25, FF-25 | 7205ATYDF | 6205ZZ |
| 30 | BK-30, FK-30 | BF-30, FF-30 | 7206ATYDF | 6206ZZ |
| 35 | BK-35 | BF-35 | 7207ATYDF | 6207ZZ |
| 40 / 45 / 50 | BK-40 | BF-40 | 7208ATYDF | 6208ZZ |
Compiled from MOSIONX 2026 general catalogue, chapter G, Table 1.1.1. For each shaft diameter, BK/EK/FK are fixed-end housings and BF/EF/FF are supported-end housings. At 20 mm there are two bearing sets: BK-20 uses 7004ATYDF / BF-20 uses 6004ZZ; EK-20/FK-20 use 7204ATYDF / EF-20/FF-20 use 6204ZZ.
Full load ratings (Cr, C0 and stiffness) are in the support-unit bearing load chart.
※ When the ball-screw shaft diameter is Ø6 mm and EK-06 or EF-06 is used, the screw must be ground grade.